Pump or rotary cutter for operation in a fluid

ABSTRACT

The invention relates to a fluid pump or rotary cutter having at least one first element ( 9′″, 10 ′″) which can be brought from a transport state into an operating state by changing at least one mechanical property. Such a pump can, for example, be a blood pump for the medical, microinvasive area. The object of achieving a transition between the transport state and the operating state which is as comfortable as possible and in so doing leaving a freedom in the design of the corresponding apparatus, in particular of a pump, which is as large as possible, is achieved using the means of the invention in that the first element at least partly comprises a material ( 24, 25, 26, 27 ) or can be filled with a material or material mixture which passes through a chemical reaction, in particular cross-linking, or a crystallization for transition into the operating state.

The invention is in the field of mechanical engineering and precisionengineering and can be used to particular advantage in apparatus whichare conveyed to a deployment site in a transport state and are therebrought into an operating state before they are started.

This is, for example, sensible with devices which have to be conveyed tosites which are difficult to access in order to be used there, forexample pumps or machining tools in contorted hose systems or pipesystems.

In the microscopic scale, such devices can be used as microinvasivedevices, for example pumps or rotary cutters in human or animal vessels,for example blood vessels or other bodily cavities.

In this respect, it is difficult to introduce these devices through thebody's own vessels since the corresponding dimensions have to be keptvery small for this purpose, with simultaneously larger dimensions beingsensible in operation for the efficiency of use.

In the field of catheter pumps, in particular of blood pumps, radiallycompressible pumps have already been proposed to solve this problemwhich are kept in a transport state with small radial extent duringtransport and which can be radially expanded at the deployment site, forexample in a ventricle, after introduction there.

For this purpose, complex and/or expensive mechanical constructions areknown which serve the erection of conveying elements of a rotor. Inaddition, it is often necessary to stabilize the corresponding conveyingelements such as conveying blades in operation since they are exposed toconsiderable fluid forces in operation.

A compressible rotor is known, for example, from U.S. Pat. No.6,860,713. In addition, a further rotor is known from U.S. Pat. No.7,393,181 B2. In the solutions known from the patent literature,provision is made in part that a rotor is compressible by elasticallydeformable conveying blades or that erection mechanisms for conveyingblades are provided which are otherwise laid at the side of the rotorwhen it is stationary.

In addition to the compressibility of the rotor, it can also beadvantageous or sensible to configure the pump housing, which cansurround the rotor, in a correspondingly compressible manner.

In this respect, there is as a rule the problem that, on the one hand,the construction and the materials of the rotor should be stable inoperation in order reliably to convey the fluid at high speeds and that,on the other hand, a certain yielding of at least parts of the rotor isdesirable to keep the forces which are necessary for the compression ofthe rotor or of the pump within limits.

A technique is known from WO 2009/132309 to bring stents into a desiredform after the introduction into a blood vessel by introducing ahardenable medium and subsequently to stabilize them in an operatingstate.

It is the underlying object of the present invention against thisbackground to configure a corresponding apparatus for a mechanicalaction on a medium, in particular on a fluid pump or a rotary cutter,such that it can be sensibly brought from a transport state into anoperating state, wherein the transport state has a particularsuitability for transport, whereas the operating state differs from thisand is in particular suitable for the operation of the apparatus/pump.

The object is achieved by the features of the invention in accordancewith claim 1.

Since the first element comprises a material or is filled or fillablewith a material or a material mixture which passes through a chemicalreaction on transition into the operating state, for example across-linking or a transition from the liquid state into a solid stateor a change in the rheological state and thus at least changes amechanical property, it is possible to implement a lower stiffness or alower viscosity in the transport state of the first element, forexample, than in the operating state. For example, the first element canbe a conveying element, for example a conveying blade of a rotor of afluid pump or a bracing element of a rotary cutter so that, on a lowerstiffness, the corresponding conveying element can be laid onto a huband the corresponding rotor is thus easily compressible. In this state,the rotor can also be self-compressible in that, in the state of rest,the conveying elements lie on the hub and are only erected on being putinto operation by centrifugal forces.

In order then to ensure a higher stiffness of the conveying blades orconveying elements in operation, the material of which the conveyingblade or a part of the conveying blade is composed is selected such thatit undergoes a hardening or stiffening when passing through thecorresponding reaction or the transition, in particular the transitioninto a different state of aggregation, for example a crystallization.

Provision can also be made that the first element, that is, for example,the conveying element, has hollow spaces which can be filled with acorresponding material, for example via feed hoses, and which can thenbe hardened, stiffened or, when it is a case of a liquid, whoseviscosity can be changed.

The change of the viscosity can be effected, for example withmagnetorheological or electrorheological liquids, by applying a magneticfield or an electric field from outside a patient's body. Acorresponding field can, however, also be effected by coils orelectrodes in the body in the direct vicinity of the pump/rotary cutter.The field generating elements can also be directly fastened to thepump/rotary cutter.

In this respect, it is not the whole element which has to change itsproperties accordingly, but it is rather sufficient, for example, if ajoint connecting the conveying element to a hub is stiffened by thecorresponding reaction or changes its shape and thereby radially expandsor erects the conveying element.

Provision can also be made that the first element represents anotherpart of a rotor of a fluid pump or that a pump housing has accordinglyto be brought into an operating shape or a stiffness corresponding tothe operation.

In this case, as with a corresponding use with a rotor, hollow spacescan also be provided which can, for example, be filled with a fluidunder pressure and can thus be inflated to give the corresponding firstelement a desired shape, whereupon the material can be hardened orstiffened to keep this shape stable.

Alternatively to the stiffness, a different mechanical property such asthe geometrical shape or size can be changed by the correspondingreaction. For example, a part of a conveying blade can be shorted orextended in the manner of a shrinking hose by the reaction and thereby,that is, by means of lever forces, erect or stiffen the conveying blade.

The material of which the first element is composed in part or withwhich it can be filled, can, for example, be a hardenable material, inparticular a hardenable plastic.

A hardening can take place for transition into the operating state, forexample by temperature effect or pressure effect, electric and/ormagnetic fields or pulses, radiation (IR light or UV light, α, β, γradiation), mechanical effect, e.g. ultrasound or vibration, or can alsobe brought about by contact with a further material or by initializationof a crystallization with a liquid material.

The further material can in this respect be a real reaction partnerwhich likewise reacts in the reaction and undergoes a conversion or itcan be a catalyst or enzyme which, when added, results in anacceleration of the reaction.

The further material can, for example, be included in the medium onwhich the apparatus should act, for example in the body fluid in which acorresponding fluid pump should be operated. In this case, the bodyfluid can diffuse on the introduction of the apparatus into a body andthe desired reaction can then take place before the start of operationeither automatically or initiated or assisted by additional measures.The first material can for this purpose e.g. comprise a protein orconsist of a protein.

It becomes possible by the invention to ensure mechanical properties forthe operation of the apparatus, for example the pump, which would bedisadvantageous during the transport to the deployment site and whichcan be avoided by the invention. These properties are only achievedafter the bringing to the deployment site with the end of thecorresponding reactions. The corresponding reactions can be reversible,but also irreversible.

An advantageous embodiment of the invention further provides that thefirst element can be changed by a continued or further reaction,reversibly or irreversibly, into a state in which the apparatus can betransported or in which it can be brought into a transport state bymechanical destruction.

For example, by continuing the reaction which was passed through beforethe operating state was reached, a further change of the mechanicalproperties can take place, e.g. by (cross-linking) embrittlement of thematerial of which the first element is wholly or partly composed. Thisembrittlement can, for example, go so far with a synthetic resin thatthe corresponding parts can break by themselves or can at least beeasily broken in order again to achieve a suitable transport state forthe return transport of the apparatus/fluid pump. A different reactioncan, however, also be provided to achieve the corresponding desiredresult.

In addition to the apparatus in accordance with the invention, theinvention also relates to a method in which the apparatus is firstintroduced into a body of a living being, wherein the material/thematerial mixture of the first element thereupon undergoes a reaction, inparticular a cross-linking, or a crystallization from the liquid phase,before the apparatus is started.

By such a handling, the apparatus is first brought to the deploymentsite within a body of a living being in the transport state and is onlythere brought into the operating state with respect to the mechanicalproperties and thus into a form efficient for operation.

Provision can particularly advantageously be made that the or a materialis introduced into at least one hollow space of the first element beforethe reaction.

For example, a hollow space or a series of hollow spaces, which can beformed, for example, by bubbles of a foam of which the first element iscomposed, can be filled via hoses with a material which can eitheritself pass through a reaction to change its mechanical properties orwhich meets a further material in the hollow spaces and reactsaccordingly with it, or wherein one of the materials serves as acatalyst for the reaction.

The actual reaction can in this respect be initiated, assisted orcarried out by a corresponding influencing from outside, wherein, forexample, radiation, temperature change, mechanical action, such asultrasound, or the action by electric and/or magnetic fields can servefor this purpose.

The invention moreover relates to a fluid pump or rotary cutter havingat least one first element which can be brought from a transport stateinto an operating state by changing at least one mechanical property,wherein the first element at least partly comprises a material or can befilled with a material or material mixture which, as long as it isexposed to a radiation or an electric and/or magnetic field, hasmechanical properties, in particular with respect to stiffness,viscosity, size and/or shape, changed compared with the state withoutsuch an action.

Examples for such a change of the mechanical properties by fields arethe piezoelectric effect and magnetorestriction or with liquids themagnetorheological effect or the change of the viscosity by electricfield effect.

A corresponding method in accordance with the invention for putting suchan apparatus into operation provides that the apparatus is exposed tothe corresponding action to make the apparatus operable after itsintroduction into a body of a living being. The action usually has to bemaintained during the operation of the apparatus/fluid pump. Neither areversible nor an irreversible chemical reaction has to take place inthis respect, but rather only a different mechanical state of thematerial is adopted in dependence on the action.

In a modification, the invention can also be configured so that thecorresponding action is maintained in the transport state and is removedor is omitted for reaching or during the operating state.

Different mechanisms usable in situ can be considered for the directchange of the mechanical properties of the mentioned elements, inparticular the elements of pumps and rotary cutters, includingmechanisms in the chemical field, in particular cross-linking.

Cross-linking in macromolecular chemistry refers to reactions in which aplurality of individual macromolecules are linked to form athree-dimensional network. The linking can be achieved either directlyon the buildup of the macromolecules or by reactions on already existingpolymers. Examples for directly cross-linking reactions are radicalpolymerizations of monomers having two vinyl functions or thepolycondensation or polyaddition using monomers having two or morefunctional groups. The cross-linking of already existing polymers cantake place either via functional groups already present in the polymerby an adroit choice of the reaction conditions (so-called selfcross-linkers) or by the addition of multifunctional low-molecularsubstances, the cross-linking agents. The hardening of epoxy resinsusing amines and the addition of substances containing sulfur on thevulcanization of rubber are examples for cross-linking reactions.

Generally synthetic resins, polyvinyl chloride (PVC), vulcanized rubber,polyethylene, PMMA, polypropylene, PET, PTFE, polyurethanes, polyesters,polyamides, polystyrene and proteins (example: keratin) are known ascross-linkable materials. The biocompatibility naturally has to beconsidered on the selection for the use in accordance with theinvention. Optionally, less suitable materials can only be used as afilling for hollow bodies.

The individual material classes in detail:

In accordance with DIN 55958, synthetic resins (also called reactionresin) are synthetically manufactured by polymerization reactions orpolycondensation reactions. They can be modified by natural substances,for example vegetable or animal oils or natural resins, or manufacturedby esterification or saponification of natural resins.

Synthetic resins as a rule comprise two main components. The mixture ofboth parts (resins and hardeners) produces the reactive resin compound.The reaction process is largely dependent on the environmentaltemperature and the material composition can often be selected so thatthe hardening reaction only takes place at a noticeable speed on aheating to body temperature. On hardening, the viscosity increases andwhen the hardening is complete a non-meltable (thermosetting) plastic isobtained.

A polymerization can also be initiated in a variety of plastics by theapplication of radiation (particle radiation (alpha or beta particles),or also X-ray radiation or gamma radiation or UV radiation). There are,e.g. in dental engineering, excellent UV-hardening adhesives which arealso correspondingly biocompatible.

Radiation cross-linking gives inexpensive bulk plastics or technicalplastics the mechanical, thermal and chemical properties ofhigh-performance plastics. This refining of plastics allows a use underconditions which these plastics would otherwise not withstand. Thehigh-energy beta or gamma radiation triggers chemical reactions in theplastic parts and thus results in a cross-linking of themolecules—comparable to vulcanization in rubbers.

The cross-linking of polyethylene, polyamide, PVC and PBT is the mostsignificant from a quantity aspect.

The cross-linking of thermoplastic elastomers (TPO, TPC and TPA) isincreasingly gaining importance. A cross-linking of polypropylene isgenerally also possible although degradation reactions predominate withthis material as a rule. The following can apply as a general rule:Radiation cross-linking is always possible when chemical cross-linkingby means of radical initiators such as peroxides is possible.

The advantage of radiation cross-linking is that the method works atroom temperature or at body temperature and at normal pressure.

The radiation for hardening takes place after or during the molding ordeforming. A direct deforming can, however, also take place by theradiation itself and by an accompanying cross-linking and desiredshrinking or stretching of the material thus treated. The advantageousprocessing properties of thermoplastics are thus combined with theproperties of thermosetting systems.

Rubber is mainly manufactured synthetically. Synthetic rubber is usuallycomposed of styrene and butadiene; other raw material bases are styreneacrylate, pure acrylate, vinyl acetate. The first commercially usableone was the styrene butadiene rubber, another is neoprene.

Polyethylene (abbreviation PE) is a thermoplastic manufactured bypolymerization of ethene.

Polyethylene belongs to the group of polyolefins. Known trade namesinclude: Alathon, Dyneema, Hostalen, Lupolen, Polythen, Spectra, Trolen,Vestolen. Polyethylene is manufactured on the basis of ethylene gaswhich can be manufactured either conventionally in a petrochemicalmanner or from ethanol.

Polyurethanes (PU, DIN abbreviation: PUR) are plastics or syntheticresins which arise from the polyaddition reaction of diolen or polyolenewith polyisocyanates. The urethane group is characteristic forpolyurethanes.

Polyurethanes can be hard and brittle, or also soft and elastic,depending on the manufacture. The elastomers in particular show acomparatively high breaking strength. In foamed form, polyurethane isknown as a permanently elastic flexible foam or as a hard expandingfoam.

Polyurethanes can have different properties depending on the choice ofthe isocyanate and of the polyol. The density of unfoamed polyurethanevaries between around 1000 and 1250 kg/m3.

The later properties are substantially determined by the polyolcomponent because it is usually not the isocyanate component which isadapted to achieve the desired properties, but rather the polyolcomponent. The following isocyanate components are generally used:

-   methylene diphenyl diisocyanate (MDI)-   polymeric methylene diphenyl diisocyanate (PMDI)-   toluene diisocyanate (TDI)-   napththylene diisocyanate (NDI)-   hexamethylene diisocyanate (HDI)-   isophorone diisocyanate (IPDI)-   4,4′-dicyclohexylmethane diisocyanate (H12MDI)

Mechanical properties can be influenced in dependence on the chainlength and on the number of branches in the polyol. A use of polyesterpolyols in addition to the more usual polyether polyols results inbetter stability because polyester polyols have a higher melting pointand thus solidify on application of the polyurethane.

The foaming of polyurethane foams arises due to the addition of water.On the reaction of water with isocyanate, carbon dioxide is split offwhich swells the foam. The volume weight of the arising foam can bevaried by the quantity of added water. Typical densities are around 5 to40 kg/m3 for soft slab foam or 30 to 90 kg/m3 for hard slab foam.

When polyurethanes are fully cured and no longer contain any monomers,they as a rule do not have any properties harmful to the health.Isocyanates can, however, trigger allergies and are suspected of causingcancer. The toluene diisocyanate used for some polyurethanes evaporatesat room temperature and can cause damage in the lung when inhaled. Suchsubstances are predominantly only used as filling of a closed hollowbody, with subsequent hardening, located in the patient's body.

Polyurethanes arise by the polyaddition reaction of polyisocyanates withmultiple alcohols, the polyols. The linking takes place by the reactionof an isocyanate group (—N═C═O) of a molecule having a hydroxyl group(—OH) of another molecule while forming a urethane group (—NH—CO—O—). Inthis respect, no splitting off of secondary products takes place such asin polycondensation.

The polyurethane formation by polycondensation requires at least twodifferent monomers, in the simplest case diol and diisocyanate. It takesplace in stages. First, a bifunctional molecule having an isocyanategroup (—N═C═O) and a hydroxyl group (—OH) is formed from diol anddiisocyanate. It can react at both ends with further monomers. In thisrespect, short molecule chains arise, so-called oligomers. They canreact with further monomers, other oligomers or already formed polymers.

Depending on the starting materials, linear or cross-linked polymers areobtained. Linear polyurethanes can, for example, be obtained from diolsand diisocyanates. Linear polyurethanes can be subsequently cross-linkedby addition of further diisocyanate. Alternatively, cross-linkedpolyurethanes can also be manufactured by the reaction of diisocyanatesor triisocyanates with polyols.

In a secondary reaction, water reacts with some isocyanate groups; in sodoing, carbon dioxide is released which allows the still soft plastic toswell. The simultaneously created primary amino group reacts with anisocyanate group to form a substituted urea.

If a specific polyurethane should be manufactured in practice, twopossibilities are available:

Direct reaction of a polyol with a polyisocyanate (a one-stage process)

Manufacturing a functionalized smaller polymer (so-called prepolymer) asan intermediate product which reacts in a second step to form thedesired polymer by cross-linking the functional groups (a two-stageprocess)

Biogenic Polyols

As a rule, both the polyols and the polyisocyanates originate from theproduction from petrochemical raw materials; however, polyols on thebasis of vegetable oils can also be used. Ricinus oil is above allsuitable for this purpose since it has hydroxyl groups itself and it canbe converted directly with isocyanates. Derivatives of the ricinus oilcan furthermore be used. Furthermore, polyols on the basis of vegetableoils can be manufactured, on the one hand, by epoxidation of thevegetable oils with a subsequent ring opening and via atransesterification of vegetable oils with glycerin. Polyurethanes onthe basis of vegetable oils are also marketed as “bio polyurethanes” dueto the biogenic origin of some of the raw materials.

Polyesters are polymers having ester functions—[CO—O—]—in their mainchain. Polyesters admittedly are also present in nature, but todaypolyesters are rather understood as a large family of synthetic polymers(plastics) which include the widely used polycarbonates (PC) and aboveall the technically important thermoplastic polyethylene terephthalate(PET). Mylar is a particular processing form of the polyethyleneenterephthalate—as a film. A further form is the thermosettingunsaturated polyester resin (UP) which is used as an inexpensive matrixresin in the field of fiber plastic composites.

The following can be considered as the polyester:

-   -   PES or PEs polyester (group name)    -   PBT polybutylene terephthalate, a derivative of terephthalic        acid    -   PC polycarbonate, a derivative of carbonic acid    -   PET polyethylene terephthalate, a derivative of terephthalic        acid    -   PEN polyethylene naphthalate    -   UP unsaturated polyester resin    -   polyamides

The designation polyamides is usually used as a name for synthetictechnically usable thermoplastics and thus delineates this materialclass from the chemically related proteins. Almost all importantpolyamides are derived from primary amines, that is, the functionalgroup —CO—NH— occurs in their repetition units. In addition, polyamidesof secondary amines (—CO—NR—, R=organic residue) also exist. Inparticular amino carboxylic acids, lactams and/or diamines anddicarboxylic acids are used as monomers for the polyamides.

Polyamides can be categorized in the following classes:

By the Kind of Monomers

Aliphatic polyamides: the monomers are derived from aliphatic basebodies, e.g. PA from ε-caprolactam (polycaprolactam, abbreviated PA 6)or from hexamethylene diamine and adipic acid (PA 66).

Partially aromatic polyamides: the monomers are derived in part fromaromatic base bodies, e.g. PA from hexamethylene diamine andterephthalic acid (PA 6T).

Aromatic polyamides (polyaramides): the monomers are derived from purelyaromatic base bodies, e.g. para-phenylene diamine and terephthalic acid(aramide).

By the Kind of Monomer Composition

Homopolyamides: the polymer is derived from an amino carboxylic acid orfrom a lactam or a diamine and an dicarboxylic acid. Such polyamides canbe described by a single repetition unit. Examples for this are the PAfrom caprolactam [NH—(CH2)5-CO]n (PA 6) or the PA from hexamethylenediamine and adipic acid [NH—(CH2)6-NH—CO—(CH2)4-CO]n (PA 66).

Copolyamides: the polyamide is derived from a plurality of differentmonomers. Such polyamides can only be described by giving a plurality ofrepetition units. Examples for this are the PA from caprolactam,hexamethylene diamine and adipic acid[NH—(CH2)6-NH—CO—(CH2)4-CO]n-[NH—(CH2)5-CO]m (PA 6/66), or PA fromhexamethylene diamine, adipic acid and sebacic acid[NH—(CH2)6-NH—CO—(CH2)4-CO]n-[NH—(CH2)6-NH—CO—(CH2)8-CO]m (PA 66/610).It must be noted that the formulae given only describe the polymercomposition, but not the sequence of the monomer units; these areusually statistically distributed over the polymer chains.

By the Kind of Softening/Solidification Behavior

Partially crystalline polyamides: form crystalline domains from the meltwhen cooling (1st order phase transition). As a rule, the whole meltdoes not solidify in a crystalline manner, but amorphous domains arerather also formed (see below). The ratio between the crystalline andthe amorphous domains is determined by the chemical nature of thepolyamide and by the cooling conditions. In addition, thecrystallization can be promoted or hindered by nucleating orantinucleating additives. Polyamides which crystallize easily are e.g.PA 46 or PA 66; polyamides which crystallize with difficulty are e.g. PAmXD6 from xylylene diamine and adipic acid or certain copolyamides.

Amorphous polyamides: solidify in glass-like manner from the melt. Inthe solid state, there is no long-range order of the repetition units.The transition between solid and liquid is described by the glasstransition temperature (2nd order phase transition). Examples are the PAfrom hexamethylene diamine and isophthalic acid (PA 61) and certaincopolyamides. Generally, amorphous polyamides include monomer unitswhich make a regular, crystalline arrangement of the chains impossible.Under extreme cooling conditions, otherwise partially crystallinepolyamides can also solidify amorphously.

Polystyrene (abbreviation PS, IUPAC name: poly(1-phenylethane-1,2-diyl))is a transparent, amorphous or partly crystalline thermoplastic.Amorphous polystyrene can be used for a variety of purposes.

Polystyrene is used either as a thermoplastically processable materialor as a foam (expanded polystyrene). Polystyrene is physiologicallyharmless. Polystyrene is predominantly gained by suspensionpolymerization of the monomer styrene which has exceptionalpolymerization properties. It can be polymerized radically,cationically, anionically or by means of Ziegler-Natta catalysts. Etheneis today acquired from crude oil. Chlorine is above all acquired on alarge technical scale in chlorine alkaline electrolysis from commonsalt. The chlorine is added to the ethene in a first step and1,2-dichloroethene is created. In a second step, HCl is split offtherefrom, with VCM arising. VCM is polymerized in an autoclave to formPVC under pressure and under the addition of initiators and otheradditives. Three different polymerization processes are essentiallyknown. The oldest process, in a historical view, is emulsionpolymerization. The initiators (for example peroxides and other percompounds) are soluble in water in this case. The so-called E-PVC isobtained. If the VCM is distributed in the water by intensive stirringand if the initiator (for example organic peroxides,azobisisobutyronitrile [AIBN]) is soluble in monomers, one speaks ofsuspension polymerization which results in S-PVC. If no water is usedduring the polymerization, one speaks of block PVC or mass PVC, alsocalled M-PVC. In this respect, the initiator is dissolved in monomericvinyl chloride.

Magnetorheological Liquids:

The liquid used, a special magnetorheological oil, is permeated withmicroscopically small, magnetically polarizable metal particles. It ispossible to generate a magnetic field via an electromagnet or apermanent magnet. The metal particles are thereby aligned in thedirection of the magnetic field and thus decisively influence theviscosity, i.e. the flowability of the oil. By applying a voltage, thearrangement of the magnetic particles and thus the physical consistency(viscosity) of the liquid reacting almost without delay is varied.

The property of the dilatancy of a substance can also be used directlyto increase the viscosity in situ. For this purpose, the effect of theso-called structural viscosity, opposite to dilatancy, will beexplained.

Structural viscosity, also called shear thinning, is the property of afluid to show a reducing viscosity at high shear forces. I.e., thehigher the shear acting on the fluid, the less viscous, it is. Such afluid is therefore aptly called shear thinning, which is occasionallyused as a synonym for structural-viscous.

The reduction of the viscosity arises due to a structural change in thefluid which provides that the individual fluid particles (e.g. polymerchains) can slide past one another more easily.

Since the viscosity does not remain constant in a structural-viscousfluid as the shear increases, it is classified as a non-Newtonian fluid.

Other fluids from this classification have the following propertiesinter alia:

Dilatancy, the opposite behavior to structural viscosity;

Thixotropy, the viscosity does not immediately increase again afterreduction of the shear force;

Rheopexy, the opposite behavior to thixotropy.

EXAMPLES

Structural viscosity: The individual polymer chains are interlinked(=interlaced) in polymer solutions and polymer melts. As the shear forceincreases, these interlinks release and the viscosity drops. This effectplays a large role in the processing of thermoplastics. Lower injectionpressures are therefore required in the preparation of thin-walledinjection molded parts than with thick-walled ones.

Non-drip wall paint does not drip off the roller since the shear issmall and the viscosity is large, whereas it is easy to apply to thewall since the thin film between the wall and the roller causes a largeshear and thus the viscosity is small.

Associative materials are systems in which small molecules congregate toform supramolecular systems via physical interactions, for examplehydrogen bridge bonds or ion-dipol interactions. These bonds which areweak (in comparison with covalent bonds) are broken open by shear, whichlowers the viscosity. The special feature in this respect is that thebonds only completely form back after a certain material-specific time(→thixotropy). Technically important representatives are ionomers.

Dilatancy (also shear thickening) is in rheology the property of anon-Newtonian fluid to show a higher viscosity at high shear forces. Adilatants fluid is also called shear thickening or shear hardening.

The increase in the viscosity arises through a structural change in thefluid which ensures that the individual fluid particles interact morewith one another (for example interlace) and so slide past one anotherless easily.

The viscosity of a dilatant fluid increases with the shear speed , butdoes not depend on the time with a constant shear speed.

If the viscosity does not immediately fall again after a reduction ofthe shear force, one speaks of rheopexy which is indeed time-dependent.

The US manufacturer Dow Corning produces the dilatant putty Silly Putty(also called Bouncing Putty, Thinking Putty, Smart Putty) from siliconepolymer which was previously above all on the market as a children'stoy. In addition to the normal kneadability, this substance behavescompletely differently on a sudden mechanical strain: if a ball of thematerial is thrown to the ground, it bounces back up like a rubber ball;if a piece is hit very quickly with a hammer, it smashes into a numberof small, sharp pieces, almost like ceramics. Sharp edges and smoothbreak surfaces also form on tearing apart. Technical applications werenot previously known.

A material with similar properties has recently been used as an activeprotection system (APS), for example in motorcycle clothing: especiallyshaped pads which contain a dilatant compound permit the free movabilityof the carrier. On an abrupt blow as a consequence of a fall, however,the material “hardens” to a hard rubber-like consistency, distributesthe acting forces over a larger body area and so prevents injuries.

Electrorheological Fluids (ERFs):

A distinction is made between homogeneous and heterogeneouselectrorheological fluids. The homogeneous ERFs comprise e.g. aluminumsalts of stearic acid. The active mechanism of the homogeneous ERFs isnot known with absolute certainty. The heterogeneous ERFs comprisepolarizable particles or droplets which are dispersed in an electricallynon-conductive carrier fluid, e.g. silicone oil or mineral oil.

Dipoles are induced in the particles by an external electric field. Theparticles form chains and columns along the field lines of the electricfield. This so-called Winslow chain model is the simplest structuralmodel to explain the electrorheological effect.

Practical Application and Areas of Use Electrorheological fluids areusually used as a central component of a mechatronic system. Thesesystems can react to different general conditions together with ahousing, a high-voltage power pack and a corresponding control orregulation.

The damping properties of hydraulic bearings can thus, for example, becontrolled by the use of an electrorheological fluid in that theviscosity of the electrorheological fluid is controllable. When such abearing is used as an engine bearing in an automobile, the damping couldbe matched dynamically to the speed of the engine and to the property ofthe ground to reduce the noise strain for the occupants.

Electrorheological fluids are just as loadable as their base materials.When used as a variable brake, modern ERFs are, unlike solid brakes, notabrasive and are comparatively temperature stable. There are, however,also ERF formulations which can be used as abrasives due to their highabrasiveness.

The research and development of the past years have resulted inconsiderable improvements both in the rheological properties and in theelectric properties of electrorheological fluids. In this respect, thedevelopment has in particular concentrated on ERFs from polymerparticles. Abrasion and wear no longer play any role with theseelectrorheological suspensions, e.g. of polyurethane particles,dispersed in a silicone oil as a carrier. The soft and elastic particleshave, on the one hand, no abrasive influence on the mechanicalcomponents of the ER systems (pumps, valves); on the other hand, theyare themselves extremely resistant to mechanical wear due to theirflexibility so that no degradation of the ERF itself is to be seen evenunder the most vigorous mechanical load.

The invention will be shown and subsequently described in the followingwith reference to a plurality of embodiments in a drawing.

There are shown

FIG. 1 schematically in a longitudinal section, a blood vessel with ahollow catheter introduced into it and a rotary cutter;

FIG. 2 schematically, a blood vessel which opens into a ventricle andthrough which a hollow catheter having a heart pump is pushed in;

FIG. 3 a rotor or a pump in the transport state;

FIG. 4 the rotor of FIG. 3 in the operating state;

FIG. 5 a further rotor in the transport state;

FIG. 6 the further rotor of FIG. 5 in the operating state;

FIG. 7 a third rotor in the transport state;

FIG. 8 the rotor of FIG. 7 in the operating state during the stiffeningprocess;

FIG. 9 a detail of a rotor with a conveying element which has a hollowspace which is partially filled;

FIG. 10 the detail of FIG. 9, with the hollow space being completelyfilled;

FIG. 11 schematically, a view of a rotor in the transport state with apump housing which is collapsed;

FIG. 12 the pump of FIG. 11 in the operating state;

FIG. 13 a rotor in the operating state in stiffened form with a housingof a pump in the operating state;

FIG. 14 the parts of the pump of FIG. 13 after a further treatment whichallows the breaking of the conveying elements;

FIG. 15 a rotor with conveying elements which is pushed through a hollowcatheter in the transport state;

FIG. 16 the rotor of FIG. 15 which is erected by withdrawing the hubinto the hollow catheter;

FIG. 17 a rotor which is erected by displacement of a support wheel bymeans of thrust elements; and

FIG. 18 a view of the thrust wheel.

FIG. 1 shows, as an example for an apparatus in accordance with theinvention, a rotary cutter 1 which is introduced at the distal end of ahollow catheter 2 into a blood vessel 3 of a human body to eliminate aconstriction 4 by cutting away deposits at the wall of the blood vessel.A shaft 5 runs within the hollow catheter 2, said shaft being configuredfor a rotation at high speed and being able to be driven by a motor fromoutside the hollow catheter.

The rotary cutter 1 is advantageously first introduced into the bloodvessel 3 in a transport state, for example in radially compressed form,and is then changed into an operating state on site which can, forexample, differ from the transport state in that the cutter head isradially enlarged or stiffened. The invention solves the problem ofeffecting this change in the mechanical properties of the rotary cutterin a favorable form after passing through the transport path.

FIG. 2 shows a further example application for an apparatus inaccordance with the invention which is in this case formed by a heartcatheter pump 6. The latter has a housing 7 in which a rotor isaccommodated which has a hub 8 and conveying elements 9, 10 in the formof conveying blades.

The pump typically has a larger diameter in operation than during thetransport in order to give it the required efficiency. For this reason,the pump is radially compressed before the introduction into a bloodvessel 11 through which it should be pushed into a ventricle 12. Then itis introduced through a sluice 13 into the blood vessel 10 and is pushedthrough up to the ventricle 12. The pump, for example the rotor and thepump housing, is then radially expanded together or each part on itsown. The invention can generate the expansion movement per se or assistit. It can, however, also only become effective after the expansionmovement in that, for example, the rotor or the pump housing isstiffened in the expanded position and is thus stabilized.

The pump can then be operated at high speeds and under high mechanicalload in that the motor 14 drives the shaft 15 at 10,000 r.p.m., forexample.

The erection of the individual elements of the pump 6 after the bringingto the deployment site in the ventricle 12 can take place, for example,in that the rotor 8, 9, 10 is set into rotation and is erected either bythe acting centrifugal forces or by the counter fluid forces which areadopted on the rotation or by both together. In addition oralternatively, mechanical apparatus such as pulls or compression devicescan also be provided which can be actuated along the hollow catheter 16from outside the patient body and which act on the pump head and therecause or assist a corresponding expansion movement. Other mechanisms arealso possible via which it is possible to work toward an expansion. Theywill be explained by way of example with reference to the other Figures.

FIG. 3 shows a view of a rotor having conveying blades or rotor blades9′, 10′ which are arranged at a hub 8′ and which are still shown in thetransport state in FIG. 3 in which they lie radially at the hub 8′.

A respective part region 17, 18 of each conveying element 9′, 10′ isdesigned such that it contracts through certain external influences suchas radiation with UV light or particle radiation, (α, β, γ radiation),electric and/or magnetic fields, ultrasound or mechanical strain. Selfcross-linking plastics which harden, on the one hand, and contract, onthe other hand, on the cross-linking can be selected as the materials17, 18, for example.

FIG. 4 shows that the conveying elements 9′, 10′ are pulled more to thehub 8′ in their regions by a contraction of the regions 17, 18 and arethus radially erected, as indicated by the arrow 19. This effect isstable and permanent with a permanent cross-linking. It is, however,also conceivable to use materials which show such a contractiontemporarily, for example by effects of magnetorestriction orpiezoelectric effect. In the last-named case, the rotor is only radiallyexpanded for so long as (or with an effect only in the transport stateuntil) the corresponding fields act. Otherwise the rotor stabilizes andthe external effect can be omitted without the rotor becoming unstable.

It is also conceivable to manufacture the whole region of the conveyingelements in the region of the hub from a corresponding material whicheither contracts or stiffens, wherein the geometry has to be selectedaccordingly to achieve an automatic erection of the conveying elementsif the erection is not achieved by another effect, for example bymanipulation by means of wire pulls or similar. If the expansion isachieved by other effects, it may be sufficient to stiffen parts of theconveying elements 9′, 10′ or the total conveying elements in that theyare manufactured from a corresponding cross-linkable material or from amaterial which stiffens under a corresponding effect. Elastomers alreadyexist, for example, which react to magnetic fields by stiffening.

A further embodiment of the invention is shown in FIG. 5 having a rotorwith a hub 8″ and two conveying blades 9″, 10″ and hollow spaces 20, 21arranged therein.

The hollow spaces 20, 21 are connected to a pressure source via a linesystem having feeds 22, 23 which extend through the hub 8″.Corresponding lines can be fed either through a lumen of the hollowcatheter or through hoses additionally arranged inwardly or outwardly atthe hollow catheter there.

A gas or a liquid can, for example, be fed into the hollow spaces 20, 21for erecting the conveying elements 9″, 10″ so that the conveyingelements 9″, 10″ are erected and tightened as shown in FIG. 6. Acorresponding pressed-in liquid in the hollow spaces 20, 21 is thensolidified either by cross-linking or by a chemical reaction with afurther material or the properties of the liquid are changed by a fieldeffect, which is, for example, possible with magnetorheological liquidsby the effect of a magnetic field and a corresponding change in theviscosity and with electrorheological properties by electric fields. Therotor is thus stabilized and stiffened at a high viscosity of theliquid.

If a gas is first pressed in, a further substance must then beintroduced to maintain the stiffening permanently. A plurality ofsubstances can, for example, also be introduced in the form of liquidsand/or gases which either react with one another after meeting in thehollow spaces 20, 21 or which are added to by a catalyst as soon as theconveying elements 9″, 10″ are erected to accelerate the reaction. If anirreversible reaction is triggered by the external effect, the effectcan be removed after the stiffening of the rotor. On the other hand, themaintenance, for example of a field, can also be necessary to maintainthe corresponding desired mechanical properties of the rotor.

The pressing of the gas into the hollow spaces can also be utilizedexclusively for the erection of the conveying elements if then otherelements of the rotor are stiffened for stabilizing this state.

FIG. 7 shows a rotor having two conveying elements in the form ofimpeller blades 9′″, 10′″, wherein each of the conveying elements hastwo stiffening webs 24, 25, 26, 27. They are still flaccid in thetransport state of FIG. 7 so that the conveying elements 9′″, 10′″ cancontact the hub 8′″.

After being brought to the deployment site, the rotor is set intorotation, as designated by the arrow 28 in FIG. 8, so that the conveyingelements 9′″, 10′″ are erected by centrifugal force and/or fluidcounter-pressure. At this time, the reaction can start for stiffeningthe webs 24, 25, 26, 27, either by radiation such as by means of aninfluencing source 29, which can, however, also be replaced by amagnetic or electric field source, or by an ultrasound source or by achemical reaction which can be triggered or conveyed by diffusing in asubstance 30 in which the conveying elements move. This substance can,for example, be present in human blood as a component of the blood innatural form before the pump is used. If this substance diffuses intothe conveying elements and meets the reinforcement or stiffening webs, ahardening reaction takes place there which stiffens the conveyingelements.

FIG. 9 schematically shows a single conveying element 31 having a hollowspace 32 which is partially filled with a liquid 33.

Provision is made for erecting and/or stiffening the conveying element31 that a gas flows in along the arrows 34, 34 through a lumen in thehub 8″″ and the conveying element 31 into the hollow space 32 and reactsthere with liquid 33 while forming a foam. An expansion by which thehollow space 32 is pressurized and inflated takes place hereby and bythe corresponding reaction. At the same time, the foam 36 is stiffened,either by the reaction or by a subsequent hardening and thus stabilizesthe conveying element 31, as shown in FIG. 10.

FIG. 11 shows a pump in the transport state having a pump housing 36 inthe form of a membrane which is collapsed and tightly surrounds thelikewise compressed rotor having the conveying blades 37. The housing 36is fastened to the end 38 of the hub 39 and is pushed in this state atthe end of a hollow catheter through a blood vessel.

If the pump head is pushed through the aortic arch and into a ventriclein a use as a heart pump, the rotor can slowly be set in motion, asshown in FIG. 12. The conveying blades 37 are erected by the centrifugalforce and/or by fluid counter forces of the blood to be conveyed, suckblood through openings at the front side of the housing 36, indicated bythe arrows 40, 41, and thus increase the pressure in the inner space ofthe pump housing 36. The membrane 36 is hereby widened and inflated andtautens tightly. At the same time, the space for the complete unfoldingof the conveying blades 37 opens so that the rotor can take up its fullrotational speed. The blood can then be pressed from the inner space 42of the pump housing 36 through the openings 43 into the blood vessel 10.

The pump housing 36 is in this respect supported on the distal end 44 ofthe hollow catheter 45, with the drive shaft 46 which ends at the hub 47also extending through the hollow catheter 45. The hub 47 is sensiblyrotatably supported at both ends of the pump housing 36.

If the operating state is achieved by complete unfolding of the rotor orof the conveying blades 37 and pumping up the pump housing 36, the pumpcan thus be stabilized in this state by hardening both of the pumphousing and of the conveying blades. This is done, for example, byradiation from outside with UV light, another radiation or ultrasound orby a chemical effect either by addition of a suitable substance startinga reaction at the conveying elements or at the pump housing or byreaction with a substance which is anyway in the blood to be conveyedand which acts as a reaction partner or as a catalyst.

Alternatively to this, a temporary stiffening or increase of theviscosity can also be provided here in the case of filling liquids byusing magnetic or electric fields.

Corresponding fields can be introduced or radiated in from outside thepatient's body or they can be applied by corresponding probes which arebrought into the vicinity of the pump or are arranged at the end of thehollow catheter carrying the pump.

In an embodiment which can also be protected as a separate invention, amotor can be arranged at the pump head, for example with a correspondingpump, said motor generating a magnetic rotary field by means of its coilwhen switched on. Since said rotary field also rotates at the speed ofthe rotor, it represents a stationary magnetic field with respect to theimpeller blades of the rotor which can therefore—in addition to thedrive function—influence the magnetorheological fluid of the rotorblades in order to stabilize them. In a further embodiment, likewiseprotectable on its own, a coil without a drive function can also bearranged at the pump head, said coil effecting the stabilization of thecorresponding rotor, wherein the rotor would be driven by a separatedrive, for example by a flexible shaft.

It is also possible for all embodiments shown in this application, aswell as also independently thereof, that electromagnetic radiation suchas light, UV radiation, infrared radiation, short waves or X-rayradiation is, for example, conducted to the pump head to cause ahardening reaction there. This can take place, for example, via asuitable optical fiber which can be conducted, for example, through thehollow catheter.

FIG. 13 schematically shows a pump head having a housing 36 andconveying blades 37 which have reinforcing ribs 48. They are typicallystiffened to stabilize the operating state, for example by cross-linkingof a cross-linkable polymer.

To solve the problems which may occur in a patient on the removal of thepump head after the treatment, it is necessary to compress the conveyingblades 37. This can be done, for example in that the rotor is furtherradiated by a radiation source 49 so that the hardening is continued byfurther cross-linking up the embrittlement. If the stiffening webs 48are embrittled, they can break on their own or can be broken simply onthe removal of the pump by retracting the pump head into the hollowcatheter 49.

FIG. 14 shows the reinforcement webs 48 within the conveying blades 37in the kinked or broken state, as the pump head is pulled back togetherwith the housing 36 into the funnel-shaped distal end of the hollowcatheter 49 by means of the drive shaft 46. The retraction can, however,also take place by other means such as pulls extending parallel to thedrive shaft 46 in the hollow catheter 49.

In the manner described, the pump head can be pulled into the hollowcatheter without any greater mechanical resistance and can be removedtogether with it out of the ventricle or through the blood vessel out ofthe patient's body.

Alternatively to the continuation of the hardening process, which wasutilized after the transport to stiffen the rotor, up to theembrittlement, a treatment can also take place which is different fromthe initial stiffening treatment. An embrittlement or a breaking can,for example, be provided by ultrasound treatment. A temperature loweringcan also be locally effected, for example, by introduction of a coolantthrough the hollow catheter 49 in order to embrittle the rotor and/orthe pump housing and to make it susceptible to breaking. It is the mostsensible in this respect accordingly only to break the rotor and toleave the pump housing intact so that any breaking splinters which mayoccur cannot enter into the bloodstream.

In FIGS. 15 and 16, a possible erection mechanism is shown for a rotorafter the transport and for the transition to the operating state.

In FIG. 15, a rotor is shown having the hub 50 and the conveying blades51 in the compressed state within the hollow catheter 52 shortly beforeit is pushed out of the hollow catheter within the ventricle in thedirection of the arrow 53. The pushing out can take place by means ofthe drive shaft 54 or by means of further wires or pulls, not shown. Inthis state, the rotor is still unhardened and movable. Once it has beenmoved out of the hollow catheter, it is also alternatively oradditionally possible, in addition to other possibilities of expansion,to retract the rotor subsequently a little in the direction of the arrow55 in FIG. 16 so that the conveying blades 51 abut the edge of thedistal end of the hollow catheter 52 by the abutment and are erectedradially in the direction of the arrows 56, 57. A hardening of the rotoror only of the conveying blades or of parts of the conveying blades canthen take place so that the rotor is stabilized in expanded form. Therotor can thereupon again be pushed out of the hollow catheter 52 in thedirection of the arrow 53 and can be pushed away therefrom to reach theoperating position. In the above observation, the housing of the pumphas been left out of consideration; however, it will be additionallyprovided in the predominant number of embodiments and will surround therotor.

FIG. 17 shows a further embodiment of a rotor having a hub 58 to whichthe conveying blades 59 are fastened. After the moving out of the hollowcatheter 60, in a similar manner as shown in FIG. 15, the rotor or theconveying blades of the rotor can be erected by a pushing up of anerection wheel 61 which is shown more clearly in the plan view in FIG.18. The erection wheel 61 is effected by pushing by means of a pluralityof thrust elements 63, 64 or by means of a hose-like element whichextends within the hollow catheter 60 and which can, for example,surround the drive shaft 65.

In the erected state of the rotor, it is then hardened and then theerection wheel 61 can be retracted into the hollow catheter 60. Theerection wheel 61 is provided with large passage openings 66 in ordernot to impair or only minimally to impair the flow relationships of thepump.

As a supplement to all the above-named examples and also usable as anindependent invention, it is moreover also possible to cause the processof the hardening and/or of the softening of the apparatus in each caseby a brief effect of a pulse, of an electromagnetic field or of asimilar influence so that the respective duration of influence islimited to the minimally required degree. The crystallization process ofthe liquid can thus, for example, be triggered by a brief mechanicalpulse, similar to the procedure with so-called heat packs. Thecorresponding crystallized medium can then be liquefied again by a brieflocal heat effect. By adding to the medium metal particles, for example,which have been excited in a corresponding field, the heat effect couldbe locally limited so much that any damage to the surrounding tissue isreduced to a non-harmful degree or is completely avoided.

The apparatus in accordance with the invention and the methods inaccordance with the invention allow the influencing of the mechanicalproperties of elements of an apparatus, especially a blood pump,introduced into a patient's body using a technically clear-cut effort sothat said apparatus can be brought into the suitable form for operationor can be provided with the required stiffness without the correspondingmechanical properties already having to be present on the introductioninto the patient's body. New design forms of correspondingapparatus/pumps thereby become possible.

1-14. (canceled)
 15. A pump for operation in a fluid, the pumpcomprising: at least one rotor blade, the rotor blade having a firstcompressed state in which the rotor blade is compressed to a first sizeand the rotor blade also having a second expanded state in which therotor blade is expanded to a second size, the second size being largerthan the first size; wherein the rotor blade comprises at least in parta material, wherein in the compressed state the material is configuredto have a first material property and in the expanded state the materialis configured to have a second material property; and wherein thematerial passes through a material conversion when the rotor bladechanges between the first compressed state and the second expandedstate.
 16. The pump of claim 15, wherein the material conversion is achemical conversion.
 17. The pump of claim 15, wherein the materialconversion is a rheological conversion.
 18. The pump of claim 15,wherein the first material property and the second material property area first and second stiffness.
 19. The pump of claim 15, wherein therotor blade has a first shape in the first compressed state and a secondshape in the second expanded state following the material conversion.20. The pump of claim 15, the pump further comprising a hub coupled tothe at least one rotor blade.
 21. The pump of claim 20, wherein in thecompressed state the rotor blade is compressed onto the hub.
 22. Thepump of claim 21, wherein in the expanded state the rotor blade extendsoutwards from the hub.
 23. The pump of claim 20, wherein the first sizeis a first diameter measured from the hub and the second size is asecond diameter measured from the hub.
 24. The pump of claim 15, whereinthe first size is a first length of the rotor blade and the second sizeis the second length of the rotor blade.
 25. The pump of claim 15,wherein the material conversion is initiated by a temperature effect.26. The pump of claim 15, wherein the material conversion is initiatedby an electric field.
 27. The pump of claim 15, wherein the materialconversion is initiated by a magnetic field.
 28. The pump of claim 15,wherein the material conversion is initiated by radiation.
 29. The pumpof claim 15, wherein the material conversion is initiated by theaddition of a further material.
 30. The pump of claim 15, wherein thematerial conversion is reversible.
 31. A method for operating a pump;the method comprising: inserting a percutaneous blood pump intopatient's body, the blood pump including a rotor blade configured to befilled with a material which passes through a material conversion;transitioning the rotor blade from a compressed state to an expandedstate; and providing power to rotate the rotor blade of the pump;wherein the material of the rotor blade undergoes a material conversionduring the transitioning of the rotor blade from the compressed state tothe expanded state, wherein the material has a first material propertyin the compressed state and a second material property in the expandedstate.
 32. The method of claim 31, the method further comprisingintroducing the material into at least one hollow space of the rotorblade prior to the transitioning of the rotor blade.
 33. The method ofclaim 32, the method further comprising applying a stimuli to the pumpto initiate the material conversion, wherein the stimuli is one ofradiation, temperature change or mechanical effect, or electric ormagnetic fields.
 34. The method of claim 33, wherein the pump is exposedto the stimuli after its introduction into the patient's body and poweris provided to the pump during the application of the stimuli; or inthat the pump is exposed to stimuli during transport.